The present invention concerns a process for the production of metal chelate-labelled peptides, metal chelate-labelled peptides obtainable by this process and the use of these peptides in an immunological method of detection.
The detection of immunoglobulins in body fluids, in particular in human sera, is used to diagnose infections with microorganisms, in particular viruses, such as HIV, hepatitis viruses etc. The presence of specific immunoglobulins in the examined sample is usually detected by reaction with one or several antigens that react with the specific immunoglobulins. Methods for the determination of specific immunoglobulins in the sample liquid must be sensitive, reliable, simple and rapid.
In recent years more and more detection systems based on non-radioactive marker groups have been developed in which the presence of an analyte, e.g. a specific antibody, in the examined sample can be determined with the aid of optical (e.g. luminescent or fluorescent), NMR-active or metal-precipitating detection systems.
EP-A-0 307 149 discloses an immunological test for an antibody in which two recombinant polypeptides are used as antigens one of which is immobilized on a solid phase and the other carries a marker group and both recombinant antigens are expressed in different organisms to increase the specificity of the test.
EP-A-0 366 673 discloses a method for the detection of antibodies in a sample in which an antibody is detected by reaction with a purified labelled antigen and with the same purified antigen in a solid phase-bound form. Human IgG is for example disclosed as an antigen.
EP-A-0 386 713 describes a method for the detection of antibodies against HIV using two solid supports in which various HIV antigens are immobilized on the two solid supports each of which is brought into contact with an aliquot of a sample and with a labelled HIV antigen wherein the presence of antibodies is detected by a positive reaction in at least one of the tests. Recombinantly produced polypeptides are disclosed as HIV antigens.
EP-A-0 507 586 describes a method for carrying out an immunological test for a specific immunoglobulin in which a sample is brought into contact with two antigens capable of binding the immunoglobulin, wherein the first antigen carries a group suitable for binding to a solid support and the second antigen carries a marker group. The marker group can be a direct marker group e.g. an enzyme, a chromogen, a metal particle, or also an indirect marker group i.e. the marker group attached to the antigen can react with a receptor for the marker group which in turn carries a signal-generating group. A fluorescein derivative is mentioned as an example of such an indirect marker group, the receptor of which is an antibody which in turn is coupled to an enzyme. Polypeptides such as the hepatitis B surface antigen are disclosed as antigens. SH groups are introduced into this antigen by derivatization which are used to couple the fluorescein.
EP-A-0 507 587 discloses a specific method suitable for the detection of IgM antibodies in which the sample is incubated with a labelled antigen which is directed against the antibody to be detected and with a second antibody which is also directed against the antibody to be detected and is capable of binding to a solid phase.
EP-A-0 199 804 and EP-A-0 580 979 disclose an immunological method of detection using antigens which are labelled with luminescent metal chelate groups in particular with ruthenium and osmium chelate groups. Immunoglobulins are used as antigens which are statistically labelled by reaction with activated metal complexes.
EP-A-0 178 450 discloses metal chelates in particular ruthenium complexes to which an immunologically active material, for example antibodies, can be coupled. The coupling is achieved by the statistical reaction of the immunologically reactive material with the metal chelate.
EP-A-0 255 534 discloses a luminescence immunoassay using a metal chelate-coupled antigen or antibody. The coupling is for example achieved by the statistical reaction of a metal chelate active ester derivative with an antibody.
WO 90/05301 discloses a method for the detection and for the quantitative determination of analytes by electrochemiluminescence using luminescent metal chelates which are coupled to (i) an added analyte, (ii) a binding partner of the analyte or (iii) a reactive component which can bind to (i) or (ii). The luminescence is measured after binding the metal chelate to activated and optionally magnetic microparticlies.
In the immunological methods for detecting antibodies known from the state of the art polypeptide antigens are usually used which are normally produced by recombinant DNA methods. However, problems may occur when using such polypeptide antigens. Thus recombinant polypeptides can often only be produced in the form of fusion polypeptides in which case the fused part can lead to false positive results in the test. In addition polypeptides produced by recombinant expression often only have a very low stability in the sample solution and tend to aggregate. A further disadvantage is that it is often not possible to selectively and reproducibly introduce marker groups into such polypeptides.
Moreover the production of recombinant polypeptide antigens involves high costs and large variations in the immunological reactivity in different lots of the recombinant polypeptide antigens can occur.
The object of the present invention was therefore to provide a process with which antigens for immunological tests can be produced in a simple and efficient manner wherein the disadvantages of the antigens known from the state of the art are at least partially eliminated. In addition the process should enable a selective and reproducible introduction of marker groups into the antigens.
This object is achieved by a process for the production of metal chelate-labelled peptides which is characterized in that a peptide having the desired amino acid sequence is synthesized on a solid phase in which (a) after the synthesis an activated luminescent metal chelate is coupled to the N-terminal primary amino group of the peptide or/and (b) an amino acid derivative is introduced during the synthesis at at least one position of the peptide which is covalently coupled with a luminescent metal chelate marker group.